More or more transport of goods is transported by means of very long trailers or vehicles on the road system. This causes more and more wear and strain on the road system. In addition this may cause that trailers or long vehicles with too heavy load for the road system are driving on the road system, which generally is not desirable, but may be detrimental in periods where the frozen ground is about to thaw. The conventional way for weighing the vehicles with load is to take the vehicle into a side lane and weigh each pair of wheels on a common axle separately on a weighing cell. This may result in that the very long vehicles must repeat the weighing process three to four times each time, dependent on the number of pair of wheels on the vehicle in question.
Moreover, it is experienced that the tire standard on such vehicles often is not good enough. In Scandinavia, it is for example often experienced that trucks and long vehicles are driving around with very worn-down tires only suited for use during the summer season, thus constituting a large hazard and risk for personnel injury and material damages, while at the same time that roads may be blocked for long periods.
Use of studded tires is an established and well known method for increasing the road grip of the tires on icy and snow covered surfaces. The method has undoubtedly a positive effect on the gripping properties as well as possibilities for passage. The use provides also undisputable advantages with respect to a traffic safety point of view.
It is also a fact that studded tires wear down the road surface more than tires without studs. This wear produces local air pollution in the form of air suspended particulate matter in the form of very fine particles and in addition increased maintenance costs. Due to this fact undertakings have been introduced, such undertakings being introduction of toll on use of studded tires. In order to document due payment of such studded tire toll, season ticket is issued or as an alternative a one-day ticket may be bought. The ticket must be visually placed on the dashboard or fixed to the front window. The purpose of this studded tire toll is in principle serving as a compensation for the detrimental effects caused by the use of studded tires. In order to reduce the detrimental effects, it has also been proposed to introduce restrictions in use of studded tires during certain period in spite of the legitimacy of such use. Use of studded tires outside the allowable window for use of studded tires or during periods will result in a fine due for each wheel with studded tire, if and when such use is discovered or observed.
To-day, the toll is collected by means of a payment of a seasonal fee, payment machines or by payment using cell phones. Analyses have shown that a very large number (10-40%) do not pay the studded tire toll. This may be due to several reasons. The risk of being spotted is low, since the traffic wardens must perform manual checking for each single vehicle when in a parked position. Since several payment alternatives are available, the warden must perform an additional manual check whether the vehicle is provided with studded tires and if there is a ticket duly placed in a visual manner in the front window. This may quite often be problematic, since the front window during winter periods when studded tires are used, often is covered by snow or ice. In addition the traffic warden must also manually check the registration number of the vehicle against a central register to identify whether the owner has duly paid the toll in another acceptable way. Hence, it is very time consuming and not very effective way of controlling.
To-day it is common practice using vehicle identification systems for collecting the toll fee when the vehicle passes through a toll station, the passing of the vehicle being registered either by electronic registration, for example by radio frequency registration or by video filming, the registered information being communicated to a central unit processing the information, identifying the vehicle and registering the owner and sending a invoice for collection of the toll fee(s).
From tests it has been found that studded tires emit high frequency sound when the vehicle with studded tires drives along an asphalt or concrete covered traffic lane. Measurements of the frequencies of the sound, caused by the tires with and without studs, have been performed, and in particular for the high frequencies, i.e. frequencies higher than around 63 Hz, the differences are detectable. Moreover, measurements have shown that ice and snow cover do have an effect on the sound picture when measuring the noise caused by from tires.
Others have performed corresponding testing of studded tires, using acoustic sensors fixed directly to the road surface or on structures such as bridges. By this solution, it is the waves through air that are used for the measurements. This method functions, but is not suitable for detecting the various vehicles or their direction of motion. Moreover, snow and ice coverage on the road surface make the detection unreliable. Hence, it is therefor a need for obtaining a more reliable method for automatic measuring and registering use of studded tires on the vehicle, in order to secure that the user of studded tires do pay for the use of studded tires and for detecting whether a driver drive with studded tires outside the dedicated period.
Likewise, it is a need for providing a method and an apparatus which in a simple and effective way can measure the weight of the vehicle while moving. Likewise, it is a need for providing a method and an apparatus that more or less securely may provide signals detecting the conditions of the decks without having to stop the vehicle for visual detection while the vehicle has stopped.